The present invention relates to a catheter intended to be introduced into a body channel and including a flexible elongate body, rigid in traction, which comprises a leaktight tubular sheath for transmitting a pressurized fluid.
For treating stenoses of the coronary arteries, esophagus, urethra, etc., for example, dilatation catheters are already known which include an inflatable balloon which is arranged at the distal end of the said catheters and which, from the proximal end of the catheters, can be supplied with an inflation fluid via a leaktight tubular sheath for fluid transmission incorporated in the catheters. Thus, when the catheter has been introduced into the body channel as far as the area of the stenosis, the balloon is inflated by supplying it with an inflation fluid by way of the sheath, and the walls of the stenosis are spread apart by the balloon so as to re-establish a satisfactory passage through the said body channel.
Frequently, the leaktight sheath for transmitting pressurized fluid is arranged, at least at the distal end of the catheter, peripheral to the latter and forms the outer surface of it. Moreover, to avoid any risk of the gas communication through the sheath being interrupted by the radial collapse thereof, the sheath is made in the form of a flexible tube, which is radially rigid. Consequently, it is not possible to give the sheath as small an external diameter as would be needed to enter small body channels or pass through stenoses blocking almost the whole of such a body channel. This therefore results either in the complete impossibility of using such dilatation catheters, so that there is no solution other than to perform major surgery in order to remove at the stenosis, or in considerable friction against the walls of the body channels (or against the walls of any tubular guide for positioning the catheter) making it difficult to advance the catheters inside the body.
When the radially rigid, leaktight sheath for transmitting fluid is incorporated inside the catheter, the same disadvantages result, because its necessarily large diameter imposes a similarly large diameter on the said catheter.
The object of the present invention is to remedy these disadvantages.
To this end, according to the invention, the catheter of the type mentioned above is distinguished by the fact that the leaktight tubular sheath for transmitting a pressurized fluid is made at least partly, particularly at the distal end, of a flexible material and has a thin wall with an irregular surface so that when the sheath undergoes radial collapse, the surface irregularities thereof leave a fluid communication remaining between the ends of the sheath.
A flexible sheath is thus obtained which, in the tensioned or inflated state (when pressurized fluid is passing through it), can present a very small diameter and which, in the relaxed or deflated state (when pressurized fluid is not passing through it), has an even smaller diameter, while nevertheless providing fluid communication along its length. When the flexible sheath itself envelops one or more elongate elements of the catheter, for example tubular elements, it will be readily appreciated that its radial size is scarcely any greater than that of the elements, even in the inflated state.
Moreover, it will be noted that because of the roughnesses of the surface of the sheath, the contact surface between the sheath and the body channel (or the tubular guide for positioning the catheter) is greatly reduced, which makes it easier to advance the catheter in the said body channel.
The flexible material from which the sheath in accordance with the present invention is made may be synthetic and for example a polyethylene, a polyamide or a polyether terephthalate. The thickness of the wall of the sheath can be from a few microns to a few tens of microns.
The thin sheath with irregular surface can be obtained by means of a flexible thin-walled tube, made for example by extrusion of the materials, being shaped hot and under pressure on a mandrel whose surface has irregularities. Such a mandrel can consist of a helical spring or the like impressing a hollow helical ribbing in the wall of the said tube. It will be noted that such a helical rib, in addition to its anti-collapse effect mentioned above, also makes it possible to increase the radial resistance to crushing of the said flexible sheath.
It will be noted that document U.S. Pat. No. 5,466,222 describes a catheter provided with internal and external bellows intended to be compressed longitudinally.